1. Field of the Invention
The present invention relates to the use of selected metal phthalocyanine colorants in phase change inks. In particular, the invention relates to phase change ink compositions that comprise the combination of at least one phase change ink carrier composition and a compatible phase change ink colorant that comprises at least one metal phthalocyanine tetraamide dye, or at least one metal phthalocyanine tetraester dye, or mixtures thereof. The invention also discloses the preparation of metal phthalocyanines, optionally or selectively, as a distribution of mono-, di-, tri- or tetra-substituted chromophores containing esters and/or amides. The present invention also relates to, as novel compositions-of-matter, selected metal phthalocyanine tetraester compounds that are useful as dyes.
2. Brief Description of the Art
Phase change inks in digital printing applications (also sometimes called solid inks or hot melt inks) have in the past decade gained significant consumer acceptance as an alternative to more traditional printing systems such as offset printing, flexography printing, gravure printing, letterpress printing and the like. Phase change inks are especially desirable for the peripheral printing devices associated with computer technology, as well as being suitable for use in other printing technologies such as gravure printing applications as referenced in U.S. Pat. No. 5,496,879 and German Patent Publications DE4205636AL and DE4205713AL assigned to Siegwerk Farlenfabrik Keller, Dr. Rung & Co.
In general, phase change inks are in the solid phase at ambient temperature, but exist in the liquid phase at the elevated operating temperature of an ink jet printing device. At the print head operating temperature, droplets of liquid ink are ejected from the printing device and, when the ink droplets contact the surface of the printing media, they quickly solidify to form a predetermined pattern of solidified ink drops.
Phase change inks are easy to use and safe. They can be easily loaded into the printer by the user, generally in the form of solid sticks of yellow, magenta, cyan and black ink having a solid consistency similar to children's crayons. Inside the printer, these inks are melted at an elevated temperature in a print head having a number of orifices, through which the melted ink will be ejected onto the desired substrate such as media like paper or an overhead transparency film. Alternatively, the melted ink may be transferred to a rotating drum and then transferred to the substrate. As the ink cools on the substrate, it re-solidifies into the desired image. This resolidification process, or phase change, is instantaneous and a printed, dry image is thus made upon leaving the printer, which is available immediately to the user.
These phase change inks contain no solvents or diluents that can lead to undesired emissions. In all, the use and specific design of the phase change ink addresses many of the limitations of more traditional ink and printing processes.
Furthermore, because the ink is in a cool, solid form at any time when the user can actually come in contact with the ink, and the ink is in a molten state only inside the printer (inaccessible to the user), it is generally safe to use. These inks also have long-term stability for shipping and long storage times.
The phase change inks generally comprise a phase change ink carrier composition, which is combined with at least one compatible phase change ink colorant. The carrier composition has been generally composed of resins, fatty acid amides and resin derived materials. Also, plasticizers, waxes, antioxidants and the like have been added to the carrier composition. Generally the resins used must be water-insoluble and the carrier composition may contain no ingredients that are volatile at the jetting temperatures employed. Also, these carrier ingredients should be chemically stable so as not to lose their chemical identity over time and/or under elevated temperature conditions.
Preferably, a colored phase change ink will be formed by combining the above described ink carrier composition with compatible colorant material, preferably subtractive primary colorants. The subtractive primary colored phase change inks comprise four component dyes, namely, cyan, magenta, yellow and black. U.S. Pat. Nos. 4,889,560 and 5,372,852 teach the preferred subtractive primary colorants employed. Typically these may comprise dyes from the classes of Color Index (C.I.) Solvent Dyes, C.I. Disperse Dyes, modified C.I. Acid and Direct Dyes, as well as a limited number of C.I. Basic Dyes. Also suitable as colorants are appropriate polymeric dyes, such as those described in U.S. Pat. No. 5,621,022 and available from Milliken & Company as Milliken Ink Yellow 869, Milliken Ink Blue 92, Milliken Ink Red 357, Milliken Ink Yellow 1800, Milliken Ink Black 8915-67, uncut Reactant Orange X-38, uncut Reactant Blue X-17, and uncut Reactant Violet X-80 or those described in U.S. Pat. No. 5,231,135.
Colored resin reaction products such as those described in U.S. Pat. No. 5,780,528 issued Jul. 14, 1998, and assigned to the assignee of the present invention, are also suitable colorants.
Polymeric colorants have also been utilized in preparing commercial phase change inks. These colorants also possess potential for use in other applications, such as gravure printing, and other types of inks and coating applications where coloration is desired. For example, the specific class of polymeric dyes are characterized by: (1) an organic chromophore having (2) a polyoxyalkylene substituent and optionally (3) a carboxylic acid or non-reactive derivative thereof covalently bonded to the polyoxyalkylene substituent, having been described in U.S. Pat. No. 5,621,022 (Jaeger et al.).
Copper phthalocyanine dyes and pigments have also been employed as chromogens for many applications requiring a cyan to a green color. Furthermore, it is known that many derivatives of copper phthalocyanine can be made. Yet, copper phthalocyanine and many of its derivatives have some shortcomings when used in phase change inks. For example, solubility and stability problems may arise when these types of colorants are mixed with certain waxy components in phase change inks. Numerous references describe their preparation, modifications, and applications. "Phthalocyanine Compounds", Moser & Thomas 1963 by Reinhold Publishing Corp. and "Phthalocyanines Properties and Applications", Volumes 1-4 edited by Liznoff and Lever, 1990, '92, '93 & '96 by John Wiley & Sons/VCH Publication are two references that describe many of these. Furthermore, many derivatives of copper phthalocyanine (CPC) are difficult to prepare. For example, a common derivatization procedure involves the chlorosulfonation of CPC to yield chlorosulfonated CPC intermediates, which can be subsequently derivatized with various nucleophiles or quenched in aqueous bases to make acid dyes. However, this class of chlorosulfonated intermediate has a limited shelf life and must be refrigerated or quickly reacted. Another class of CPC derivatives is carboxylic acids of CPC. See U.S. Pat. No. 4,450,268 with Achar et al. as named inventors and Achar et al., Indian Journal of Chemistry, Volume 27A, May 1988, pp. 411-416. While these carboxylic acids of CPC have better shelf life and can be made easier than the chlorosulfonated CPC derivatives, their commercial feasibility, as well as commercial feasability of their intermediates and derivatives, have not yet been fully explored.
Certain phthalocyanine tetraamide compounds are known as filter dyes and useful in photoresist applications. See Japanese Kokai 09/249,814, published on Sep. 22, 1997, with Yoriaki Matsuzaki, Hirosuke Takuma and Ryu Oi as named inventors and assigned to Mitsui Toatsu Chemicals, Inc. This patent is referenced as Chemical Abstracts 127:308427m.
The present invention seeks to retain the known advantages of phthalocyanine chromogens (e.g., outstanding lightfastness and thermal stability) while overcoming the insolubility of phthalocyanine pigments and short shelf life problems of chlorosulfonated CPC intermediates, as well as eliminating the above-noted manufacturing disadvantages of their preparation. Furthermore, the present invention provides dyes with good cyan coloration, as well as allowing for easy tailoring or modification of the physical and mechanical properties of this class of colorants (e.g., making the dyes more resin or wax-like).